Significant variations in demographic features, inbreeding levels, political organization, agricultural practices, warfare intensity and rates of population growth and dispersal are known to exist among the Yanomamo Indians of Southern Venezuela and Northern Brazil. These have been partially documented in previous work by the Principal Investigator in two major population blocs that contain several historically-related villages each. Of major theoretical interest for understanding both biological and cultural evolution during the Paleolithic and Neolithic Eras is the fact that the Yanomamo social system, embodying the most frequently found elements of organization in the primitive world, seems more complex in areas where intervillage warfare is most intense and that populations in those areas are expanding at a higher rate than populations elsewhere in the tribal area. Correlated to the high growth rates is the fact that higher levels of inbreeding occur, suggesting that there is a correlation between amount of inter-personal relatedness and within-group village solidarity: the most rapidly growing populations also have the largest villages. Work proposed for the next three years will result in the documentation of these variations in additional population blocs adjacent to those already studied by the Principal Investigator, with additional foci on the ecological dimensions of the processes of population growth and expansion: Yanomamo warfare is not convincingly relatable to shortages in agricultural or other resources. Five researchers are currently studying the energetics of agriculture, protein capture and demographic variability.